How did you build it? The flying weight of the GWS 350 powered I fly is 15 oz with 18 oz of thrust. I can hold it over my head and drop it and it takes off, the stock instuction version takes quite a bit more effort, even with lipos. If your unfamiliar with launching a plane like this, I would suggest having a helper thats knows how to hand launch. A slight running start with a good overhead toss, the planes angle should be no less than parallel to the ground when released, but only about 15 degrees max. You don't want to throw it into the ground or stall it at release, it's good to have some reaction time to save it. Airflow over the wings and a good airspeed to start off with at launch is important for the heavier versions. My favorite prop for spd 400 is the GWS DD 7x3.5, made a huge difference on many of my spd 400 planes.